The present invention relates to a recording device and an adjustment method of the recording device, and is applicable to a portable type video camera that records a result of image pickup on an optical disk, for example. When an audio signal obtained by an external microphone is to be recorded, the present invention sets the characteristic of a corresponding correction circuit on the basis of a correction parameter for the external microphone which parameter is obtained from the external microphone, so that even in the recording using the external microphone, the audio signal can be simply and surely obtained and recorded with a desired sound collecting characteristic.
Of conventional, portable type video cameras that record a result of image pickup and an audio signal on an optical disk, video cameras that record audio signals obtained by an incorporated microphone as a 5.1 multichannel audio signal on an optical disk are provided.
Of such video cameras, there are video cameras that obtain audio signals from various directions by a plurality of microphones and generate a 5.1-channel audio signal by arithmetic operation processing on these audio signals. The characteristic of each microphone and the characteristic of a signal processing circuit for processing an audio signal from each microphone are adjusted at a time of shipment from a factory. Thereby the sound collecting characteristic of the audio signal obtained from each microphone is set to a reference sound collecting characteristic to create a highly realistic 5.1-channel sound field. The sound collecting characteristic is various characteristics of the audio signal that affect the creation of such a multichannel sound field, the various characteristics including directivity, frequency, sensitivity and the like.
In adjustment at a time of shipment from a factory, characteristics necessary for correction are obtained in advance from the sound collecting characteristic of an audio signal output from a microphone, and a correction parameter is set in a correction circuit provided to a signal processing circuit or the correction parameter is set in a program for circuit adjustment in order to secure the characteristics necessary for correction. Thus this kind of video camera sets the sound collecting characteristic of an audio signal from each microphone to a reference sound collecting characteristic and thereby corrects variations between microphones, and the like.
Various methods are proposed in Japanese Patent Laid-open No. Hei 6-292293, for example, in relation to such microphone characteristic correction.
There are cases where such a video camera records an audio signal by an external microphone desired by a user in place of an incorporated microphone. However, such an external microphone often has a different characteristic from that of an incorporated microphone. Therefore an audio signal with a desired sound collecting characteristic may not be obtained when the audio signal is simply obtained by an external microphone in place of an incorporated microphone. It is thus difficult to record an audio signal for creating a highly realistic sound field. Resultingly external microphones that can be used are limited.
One conceivable method for solving this problem is to adjust a video camera according to an external microphone. Specifically, as shown in FIG. 14, with an external microphone 2 connected to a video camera 1, the external microphone 2 and a sound source S are disposed in a predetermined characteristic adjusting position. A reference signal is reproduced by the sound source S, and sound is collected by the external microphone 2. The external microphone 2 includes a microphone unit 3 as a mechanical-to-electrical transducer unit for converting change in sound pressure into an audio signal and a peripheral circuit 4 for performing amplification and the like of the audio signal output from the microphone unit 3. Incidentally, depending on a type of microphone unit 3, a driving circuit for driving the microphone unit 3 is further provided in the peripheral circuit 4. The video camera 1 includes for example a correction circuit 5 for correcting the characteristic of the audio signal output from the external microphone 2 and a signal processing circuit 6 for processing the audio signal whose characteristic is corrected by the correcting circuit 5. In this adjustment, the characteristic C1 of the correcting circuit 5 is set such that the audio signal S1 output from the signal processing circuit 6 has a desired sound collecting characteristic. The correcting circuit 5 includes for example an amplifier circuit for amplifying the audio signal, an analog-to-digital converter circuit for subjecting the audio signal to analog-to-digital conversion and outputting audio data, and a filter circuit for setting the frequency characteristic of the audio data. The signal processing circuit 6 performs processing for, for example, setting the directivity of an audio signal to a desired directivity by arithmetic operation processing between the audio data and audio data obtained from other microphones.
Thus, as shown in FIG. 15, even when the external microphone 2 is used, an audio signal with a desired sound collecting characteristic can be obtained, whereby a highly realistic sound field can be formed.
In this case, however, the adjustment is a troublesome task, and some users may not be able to perform such adjustment work. While a method is conceivable in which such an adjustment mechanism is provided on the external microphone side, there is a similar disadvantage in this case.